Seven downlink transmission modes are provided in the LTE R8 protocol:
transmission mode 1: single-antenna mode based on single-antenna port 0;
transmission mode 2: transmission mode based on multi-antenna transmission diversity;
transmission mode 3: large-time delay open-loop pre-coding;
transmission mode 4: closed-loop space multiplexing;
transmission mode 5: multi-user multiplexing;
transmission mode 6: pre-coding closed-loop rank=1;
transmission mode 7: beamforming based on antenna port 5.
A transmission mode 8, which refers to perform double-stream beamforming by using antenna ports 7 and 8 is further added in LTE R9 protocol besides the seven transmission modes provided by R8. However, in terms of layer mapping, multiplexing supports the mapping of one stream to two layers at maximum, and diversity supports the mapping of one stream to four layers at maximum.
It is specified as follows in R8 rate matching process:
      N    IR    =      ⌊                  N        soft                              K          MIMO                ·                  min          ⁡                      (                                          M                DL_HARQ                            ,                              M                limit                                      )                                ⌋  
wherein, Nsoft is total soft channel bit; KMIMO is equal to 2 at transmission mode 3 or 4, otherwise KMIMO is equal to 1; MDL—HARQ is the maximum re-transmission times of downlink HARQ; Mlimit is a constant.
Then, the capacity of the circulating Buffer can be calculated by using the calculated value of NIR; in calculation of the length of output data, E=NL·Qm·┌G′/C┐;
wherein, E is the length of output data; NL is layered parameter; Qm corresponds to modulation manner; G′ is the number of symbols of useable transmission blocks; C is the number of code blocks of one transmission block; when the transmission block is mapped to one layer for transmission, NL is equal to 1; when the transmission block is mapped to two or four layers, NL is equal to 2.
It is specified as follows in R9 rate matching process:
KMIMO is equal to 2 at transmission mode 3, 4 and 8, otherwise, KMIMO is equal to 1; the rest parameter values are the same as those in the corresponding situation of R8.
Since the multiplexing supports the mapping of one stream to two layers at maximum, and the diversity supports the mapping of one stream to four layers at maximum in terms of layer mapping in R8 and R9, therefore the specified values of KMIMO and NL correspond to the above layered solution. While in R10, the multiplexing is required to support the mapping of one stream to four layers at maximum, so the original weights KMIMO and NL for rate matching in R8 and R9 are no longer adaptable to the mapping manner in R10, thus the rate matching calculation weights need to be adjusted.